The objective of the proposed research is to achieve an understanding of how a transition metal ion may interact with a reactive sulfur-containing molecule and influence the lability of the sulfur atom in reactions with nucleophiles and electrophiles. The studies will investigate the types of sulfur moieties which have been proposed to participate in sulfur transfer reactions in certain molybdoenzymes. New molybdenum complexes which contain persulfide or terminal sulfido ligands will be synthesized in this study. The complexes will be characterized in order to determine: 1) the types of sulfur ligands which participate in sulfur transfer reactions; 2) the possible bonding interactions between reactive sulfur atoms and metal ion; 3) the site(s) of nucleophilic attack on the molybdenum-sulfur complex and the resulting products; 4) the site(s) of electrophilic attack on the molybdenum sulfur complexes and the resulting products. Nucleophiles such as CN-, PR3, SO3-2, and alkyl will be employed. These may abstract sulfur or they may coordinate to the metal complex. Electrophiles such as H ion and alkyl ion will be employed.